Remote tuning control means



Feb. 17, 1942. H. REHDER REMOTE TUNING CONTROL MEANS Filed July 18, 1939INVENTOR.

. HA/V: REHDER ATTORNEY.

Patented Feb. 17, 1942 2,273,537 REMOTE TUNING CONTROL MEANS HansRehder, Berlin, Germany, assignor to Telefunken Gesellschaft fiirDrahtlose Telegraphic m. b. H., Berlin, Germany, a corporation ofGermany Application July 18, 1939, Serial No. 285,217 In Germany July18, 1938 3 Claims.

There are many cases in practice where an impedance, say, a frequencygoverning element of an oscillator must be varied from a distant point.In past practice variable reactances such as rotary condensers arefrequently employed for this purpose, and these are adjusted and set bymechanical means such as cord or cable drives or else by electricallycontrolled motors. Arrangements of this kind are comparativelycomplicated in their construction and arrangement; they also arerelatively sensitive to shock and other rough treatment. Moreover, thepresence of mechanically moving parts is often an unfavorable factor insuch remote controlled tuning devices. a

Now, the present invention discloses an arrangement adapted to act uponand vary impedances in which the above mentioned drawbacks are absent.The arrangement of the invention comprises a photo-electric cellconnected in parallel and/or in series relationship to the impedances tobe varied, the electrical data thereof being varied by the intensity ofillumination. An arrangement of this nature preferably is so designedthat the photo-electric cell according to the invention is accommodatedconjointly with a lamp inside a common opaque casing or housing, thevolume of light being given off by the lamp being acted upon either byvariation of the lamp current or by the aid of a variable stop orshutter (diaphragm) interposed between the light source or lamp and thephotoelectric cell.

In what follows an exemplified embodiment of the invention shall bedescribed in more detail by reference to the drawing. Suppose theproblem is to make an RF oscillation circuit compris ing a capacity Iand inductance coil 2 tunable from a remote point inside a certain rangeor band of frequency. For this purpose, according to the invention, byway of a coupling condenser 3 a photo-electric cell 4 is connected inparallel relation to part or whole of an inductance coil contained inthe oscillation circuit. The photoelectric cell together with anincandescent lamp 5 is confined inside a common light box (indicated bybroken lines in the drawing), the light given off by the glow-lamp beingcapable of beits intensity at will. As a result the capacity or theinternal resistance of the photo-electric cell is altered, and this, inturn, results in a change in the tuning condition of the oscillationcircuit I, 2. In lieu of the potentiometer, it would, of course, also bepossible to use a series resistance or rheostat in order to avoid wastedleak current. The said resistance or potentiometer may be soproportioned that there results a straightline frequency dependence.

The volume of light striking the photo-electric cell may be varied byvariations of the size of an iris type diaphragm interposed between thephoto-electric cell 4 and the glow-lamp 5 rather than by variations ofthe potentiometer or series resistance. It is also possible to use thearrangement here disclosed at a great many other places of a circuitorganization with a view to causing a change in the frequency. Forexample, a photo-cell may be included in the grid or plate circuitcomprising thermionic tubes if the frequency is a function of the gridor the plate potential. Also an arrangement according to the inventionmay be used in connection with a reat many arrangements where the chiefdesideratum is to produce distant or remote actions or variations of thevalue of an impedance.

I claim:

1. Means for controlling'from a remote point the tuning of a parallelresonant circuit consisting of fixed inductance and capacity, comprisinga photo-electric cell, means including a condenser for coupling saidcell in parallel to at least a portion of the resonant circuit wherebythe electrostatic capacitance of the cell is reflected into the circuit,means including a source ,of light adapted to direct a steady,uninterrupted light beam upon said cell to control the effectivecapacitance of said cell, the intensity of said light source determiningthe amount of capacitance reflected into the circuit and consequentlyits tuning, and means at a remote point for varying the intensity ofsaid light source.

2. A' system as defined in claim 1 wherein the photo-electric cell andthe light source are confined within an opaque compartment.

3. A system as defined in claim 1 wherein the means at the remote pointconsists of a source of energy and a potentiometer connectedthereacross, and connections from one end and a variable tap on saidpotentiometer to the light source.

. HANS REHDER.

